SE543508C2 - Biocomposite material comprising cellulose fibers and a bioadditive from cereal husks or barns - Google Patents

Abstract

The present invention relates generally to biocomposite materials made of cellulose and wheat bran and/or oat husk, prepared by methods comprising mixing the husk or bran with an aqueous alkaline solution, stirring and/or homogenizing the mixture, admixing with cellulose pulp and thermoforming the material under conditions admitting curing, thereby obtaining improvements in strength measured as at least one of strain at peak (%), stress at peak (%) and Young’s modulus (MPa).

Description

\ N .\ __, ,.\\,.\,_\..,, u... =.._..\___\\\\ S p.,\ . ,.\\\ \, U ~ ~ :N "Ah N ,-~ MA-- \.-\_.-~ : "w = :\\_.-=\-: .LA Technical field The present invention relates generally to biocomposite materials made of celluloseand wheat bran and/or oat husk, and methods to produce such materials.

Backqround of the invention Wheat bran and oat husk or hulls are two interesting cheap waste stream materialsfrom the agriculture industry with a big potential to be used in future sustainablematerials. Both the low price and their availability are attractive factors together withtheir esthetic properties as part of the final products. ln the publication by A.Rahmanet al. in J. Renew Mater. Supplement June 2017, pp 63-73, different ways of treatingwheat bran are analyzed and compared. lt was observed that both sodium hydroxideand sulfuric acid solubilized hemicelluloses and the remaining fractions were analyzedfor cellulose lignin, starch, fat and protein. However, no particular guidelines aredisclosed on how to produce improved biocomposite materials beyond generallysuggesting the usefulness of the fibers resulting from the treatments as a suitablereinforcing material. Several documents disclose oat husks useful either alone or asan additive to cellulose fibers to make composite boards. US675234 discloses boxboards from oat husks cooked with lime. EP1967338 discloses a board materialcomprising unprocessed oat husks and wood chips, fibers or strands compressed witha binder. EP 976790 also discloses a process to make a composite from cereal brans,husks or hulls in a thermoplastic processing step with a bonding agent. lt thereforeremains to provide a composite material of cellulose and wheat bran and/or oat huskthat can be processed with conventional methods and paper making processes withoutany additional adhesive binders, while improving the mechanical properties comparedto a composite material of cellulose fibers alone. The present invention is directed such a process and a resulting molded biocomposite product Description of the invention lt is an object of the present invention to provide improvements in compositematerials by decreasing the use of costly fibers (reduce costs), increase or at leastmaintain the mechanical properties and at the same time provide an esthetically appealing appearance of the products. lt is an object of the present invention to accomp|ish the improvements underconditions and with methods that are conventional in pulp industry and manufacturing and that are compatible with the wet end of pulp and paper production. lt is an object of the present invention to accomp|ish the improvements in compositematerials without employing a chemical binding agent or the addition of adhesives. lt is also an object of the invention to provide compatibility with currently usedchemicals and conventional procedures known in the art of pulp and paper production.

Generally the invention is directed to biocomposite materials and methods ofproducing such materials, wherein the method includes a pretreatment step of thebrans and husks or hulls in order prepare a bioadditive to be added with cellulosepulp or fibers from wood, as prepared with conventional process.

A biocomposite material in this context has the usuai nteaning ef compositematerials tfvhieh is a inaterlai anade frem tvve er mere censtituent materials frem riaturai er bieleglcai sources with different that, tft/hen combined, produce a rnaterial with cliaracterlstice different 'front at least ene efthe indlvlduai eempertertts, ln the context of the present invention, brans and husks or hulls has the meaning ofthe outer shell or coating of a seed fruit or vegetable, especially from cereals, such asthe bran hard outer layer of cereal grains. The cellulose used with the present inventiontypically comes from wood, plants, agriculture of vegetables, fruits, algae, fungi,bacteria and tunicates. ln a first general aspect, the invention is directed to a biocomposite material comprising cellulose fibers and a bioadditive from ' husks or brans; _ ..,... . tv» a... .aut 'èxVtï \.\:~\ '_ ~ *à ~ "w åššàïè. w: išš! L.- š _, ' . e ~, ._* \.~~~\\.~~ .~\.-\~'\~'\~\_~r\-\^3\*l\ Ni ~ min: ttašx.=tt.~;t«==:äšie ett _ .'-\v'\ ~'\~' \'\~' ' \\'\'\' *\\~"\ -'*\ u' u' n"ha: t,.,.~:\.-\};\=:::àë;\>. «' R^?\ L? 'will +i\'"\i'\'\ "Ö ~*'\I'\*'\~'\ CEÖÉQ *'\*'\ k*: : :\.1\.:\.- i: \.~"i i i :få .\-*.~ \.>.\.-\=Ä\.~\.- L-kß: =*¥=^=~_= at least the same strength as the corresponding material comprising same cellulose fibers in the same amount, but without the _ _~._ _.\_.~_,-~-;_.__,._ ,-_: _.\ A.- \ .__ ___, ...___~ _ _ __. _ _ _ -g __.«_ _ . w _ \ _.w _~\-_ _~\ __ __ _«_ _-\ _ _ ~\ S,e.N...Hdda.Db ,.»-and wherein the strength is measured as at least one of strain at peak (%), stress at peak (%) and Young's modulus (MPa). »ln this context, the term "free from any additional binder " means that the biocomposite does not include any conventional chemical and/or adhesive agent conventionally employed in the production of composite materials, such as í¿acrylic, styrenated butadiene copolymers, acrylates, vinyl copolymers ^* acrylics, polyvinyl acetate, vinylacrylics, ethylene vinyl acetate, styrene butadiene, poly vinyl chloride and ethylene/vinyl chloridejs, epoxy, polyester or phenolic resins and isocyanates. The skilled person will accordingly readily give the term binder-free a significant meaning. Preferably, in this first aspect, the biocomposite material comprises a bioadditive derived from at least one of wheat brans and oat husks. Preferably, the biocomposite material comprises 75% (wt) or less of the bioadditive, preferably 5 to 50% (wt). ,~»~ _- .~\ v; _-_ :w_ _» _ _: »___ .___.___.._.._«._.\____\__.,"__mh_\\\____..____.\\ N __\ _ _ , _ _ . , _ __.\ _ _.\ ,__ ~.__.\ _ __ .\ __ "___ t ___* __\ _.\ ___ ,__ __ _ ___? _ "_ _ _. ,__ _.\ __: ,_\ __ = .__1: > _. s _ _ _~ -'\ v*_~> \_-_ ' __ _»_ _\_ ___ _»_ _ _»__._. x_.~__~_«\_~__=_-_ \_ __» ___~_ _»__~___.~ _ - . __ _ ___. :__-m _\_~_ __ ...___ .__ ___ __._._,.\._:._;____._ ___ _.._____=___~;_~.:__._._ .__~_._,.____._ ___ __. ._._=,.-._ .__ _-\'\ .N _* ~*\ _ _ »N l .;.. ,__ __ 5 ___, .___ __' " \-^ \.^ _ _ ^ .-\ vw _~\ fy _ _ w _~\,- ; --.~ : .- .__ __ ___: _f_.-_ _ \«\ \_~ _ \ \w ~\:~=__ ._ __» .___ .__-___ ___; ._ .___* __~\ r \_ \_ \-'\_~ _ ï~\ -\ «\~ _._ .~ ~ _ I-x .~ ___ x. _ __~__.__ ___« .__._ _ _._s> \__._\.__.«_ ___ ~ ____: ._ __ .._. __._ s>___~__ _ _ __\_\_ .v__~ _-> _ _ f _. __ .«\_.-__~ __=\.«_ __. _ _._~_ _ _ :__- ïw:_..._.____:AN._._~_."Q_..__\__._____»___M..._\_._.\"____\a__»__ \_.___._ v!.__»___\ _ _ :__ \__: _.._____.__3.___.___»_____» _i ___.Ü.__.oh\w__..__ ._____...____\.s,»__ .__»v»v Ht:\_....____..___._.._..._____.___..\ .___.__. __ . zwfi.._..\\.._\ «\ : _~\ _-_ _«.-\ _~~~ __.- __! .>\ .~\___ Å»___..Üf..___Ö\\.__\.___ _.__x_._.__..__...__Üo.,.___._~_.Ü. _ ___.»_:5. .s.»___. _5__ _'~.-_ _-__~.~__.: _ a __~ ¿._.__:\.~ _ _~ :__-_ _- _ . \,_ _ _~ _,_ __; ln the process, the aqueous i _ k I_-\»~ »\__»~__-\_- __ ;:-_ »___-_ ._-«-,\_'« »___- _'«,_ _ ___~\-_ ;_-._ .w- _. _....__"H\\.._\\_.___. .___._..__..v.___.\_v_s\»__:__._.___. ~__.~~~._.. ._ ___ __: ..~_._\_-\.«..\_~ alkaline solution preferably comprises least 0.5% (wt) NaOH, more preferably 0.5 to5% (wt) NaOH. The forming of the biocomposite can be performed with a mouldedpulp process or a paper making process as conventionally employed in the field oftechnology. For example, useful moulded pulp processes (MPPs) are classified byInternational Molded Fiber Association (IMFA) as "Thick wall", "Transfer moulded","Thermoformed (Thin Wall)", and "Processed", see also Moulded PulpManufacturing: Overview and Prospects for the Process Technology Didone, Mattia;Saxena, Prateek; Meijer, Ellen Brilhuis; Tosello, Guido; Bissacco, Giuliano;McAloone, Tim C.; Pigosso, Daniela Cristina Antelmi; Howard, Thomas J. Publishedin: Packaging Technology and Science Link to article, DOI: 10.1002/pts.2289Publication date: 2017. ln one aspect, the above disclosed processes comprise a thermoforming step. : »w m;- \ ex .~\ w -\ > »w. _. _ . . ln aspect of the inventive process, it comprises collecting the water soluble fraction ofthe bioadditive prepares and admixing it with the dispersion of cellulose pulp. ln one aspect of the processes as mentioned, the ratio of cereal husk or bran toaqueous alkaline solution in the mixing step is from at least 1:1 to 1:100, preferably1:3 to 1:20, and most preferably 1:5 to 1:10. Preferably, the mixing step comprisesstirring and/or homogenization wherein the rpm is 30000 rpm or less. For examplethe rpm can between 5000 and 30000. ln one aspect of the processes as mentioned, the cereal husks or brans are selectedfrom at least one of wheat brans and oat husks. ln one aspect of the process an additive is added selected from at least one ofcationic starch; AKD (alkylketene dimer); ASA (alkenylsuccinic anhydride); PLA (polylactic acid); dyes; fillers; pigments; wet strength increasing agents; defoamers;preservatives; biocides and other conventional agents used in pulp industry such asclays, waxes and similar agents. Such an additive can added either in the pre- treatment step when providing the bioadditive or the admixing step between cellulose fibres and bioadditive, or in both steps of the earlier disclosed processes.

Finally, the invention is directed to a biocomposite material as disclosed produced byany of the mentioned processes.

Detailed and exemplifvinq description of the invention ln the following, a detailed description of invention methods and products are outlinedtogether with embodiments of the invention. Wheat bran and oat husk containscellulose, lignin, hemicelluloses (xylans and arabinoxylans), phenolic compounds suchas ferulic acids, minerals and proteins. The mechanical and alkaline pre-treatmentsfacilitates the extraction of the hemicelluloses and present invention exploit theirpotential as a bioadditive to contribute to an increase in mechanical properties of theproduced biocomposites. Several different methods of preparing bioadditives with pre-treatments were tested and different cellulose fibers were also investigated. All the experiments are summarized in the tables below.Different pre-treatments Reference: 25 g of CTMP was disintegrated in 2 L of tap water at 30.000 rpm using aPTl Austria disintegrator. Hand sheets were made using Rapid Köthen. After formationthe wet hand sheets were pressed with 10 tons pressure for 5 minutes and dried for10 minutes at 95°C. Final oven drying at 170°C for 5 minutes. Mechanical properties was measured using a Testometric M25-2.5AT.

Pre-treatment: Pretreatment of wheat bran from Lantmännen was performed accordingto the table below. An lka Ultra Turrax was used for the mixing of 5 g wheat bran with35 g of water containing the different chemicals in Table 1. The mixing time was 30min and the speed was adjusted to 2 different levels. After the mixing was completedthe wheat bran was added to the CTMP pulp. Hand sheets were produced exactly thesame way as the reference except that 20 g CTMP instead of 25 was used. cTMP (g) Wheat bran Additive (g) Procedure Mixing speed j-l) 20 5 2% NaOH separated 6.000filtrate j-2) 20 5 2% NaOH Wheat bran 6.000fraction Weight (g) Strain at peak (%) Stress at peak (MPa) Young's modulus (MPa) a) 23.4 2.088 (0.383) 10.34(1.254) 721.22 (46.605)b) 22.63 2.336 (0.218) 14.05 (0.706) 905.6 (29.431)c) 22.54 2.627 (0439) 17.25 (1.80) 974.66 (48.69) g) 23.13 2.032 (0393) 12.54 (179) 785.629 (36.78) 19.60j-2) 21.19 2.564 (0.237)1.978 (0.214) 19.26 (0.974)12.38 (0.987) 1129.8 (41.041)842.91 (24.180) No increase in strength was observed for the non-pretreated wheat bran withoutmechanical stirring (a, table 2). However, compatibility between the fibers and thewheat bran was good and the reduction in fiber usage was about 20%. Mechanicalmixing alone of wheat bran without additives increased strength (b and c, table 2).More intense mixing gave higher strength for the hand sheets. Sodium hydroxide pre- lls treatment (0.5%) gave higher strength compared to neutral conditions. Also here theamount of mixing had an effect on the strength. More intense mixing gave strongerhand sheets (d, e and f, table 2). Acidic pre-treatments had no effect on the final strength (h and j, table 2). ln one experiment (j-1 and j-2, table 2), the particles wereseparated from the solution after the 0.5% sodium hydroxide pre-treatment. Handsheets were made from both the solid fraction and the water soluble fraction. lt is clearthat most of the strength increase comes from the dissolved material from the wheatbran pre-treatment (j-1, table 2). Hemicelluloses such as Arabinoxylans are probablyextracted from the wheat bran during the pre-treatment and these polysaccharidesadsorb to the cellulose fibers in the "wet end" during the paper making, with improvedmechanical properties of the produced hand sheets. Different sodium hydroxideconcentrations did not have a significant effect on the hand sheet strength (k, I and m,Table 2).

Different fibers Wheat bran was treated with 0.5% NaOH. A Water-wheat bran ratio of 7:1 was used.Mixing was performed at 20.000 rpm for 30 min using an lka Ultra Turrax. 40 g of thispre-treated wheat bran was mixed with 20 g of different pulps according to the Table 3below. Hand sheets were produced as described in the section above. 20 g of the pulptogether with the pre-treated wheat bran was disintegrated in 2 L of tap water at 30.000rpm. Hand sheets were made using Rapid Köthen. Afterformation the wet hand sheetswere pressed with 10 tons pressure for 5 minutes and dried for 10 minutes at 95 °C.Final oven drying at 170 °C for 5 minutes. 25 g of pulp was used as a reference withoutwheat bran.

Wheat Weight Strain at Stress at Young'sbran (g) peak (%) peak (MPa) modulus (MPa)(%)CTMP - 24.14 2.14 11.21 760.7CTMP 20 21.92 2.6 17.42 989 Unbleachedsoft woodkraft pulp 24.80 2.86 16.27 1136.1 Unbleachedsoft woodkraft ul 22.93 4.75 26.86 1512.1 (Domsjö) Dissolvingpulp(Domsjö) 22.28 3.09 9.46 642.5 AbacaCeltex BTCF 24.61 4.72 21.52 1142 AbacaCeltex BTCF 22.61 .62 27.57 1343 Table 3: A strength increase was observed for all the pulps with pre-treated Wheat bran.

Different additives together with pre-treated wheat bran The table below (Table 4) describes how different additives added in the "wet end"together with CTMP pulp and pre-treated wheat bran affects the final compositematerials. Cationic starch further improves the mechanical properties compared to thewheat bran reference. AKD added as an emulsion also improved the strength anddramatically improved the hydrophobicity resulting in a Cobb60 value below 20. Oldwheat bran containing preservatives stored for two months at room temperature gavelower strength increase compared to freshly prepared pre-treated wheat bran. Thereason for this could be that the polysaccharides improving the strength, degrade overtime. Antifoaming agent (Dispelair CF56) in the formulation lowers the strength of theproduced hand sheets.

Additive CTPM Wheat Weight (g) Strain at Stress Young's CobbamOUM bran peak(%) at peak modulus 60(MPa) (MPa)Ref - 20g 5g 21.92 2.6 17.42 989 896(80% (20%))Cationic 0.3 g 20g 5g 22.47 2.92 23.75 1275 -starch (80% (20%)(solbond )PC170)AKD 0.8 g 20g 5g - 2.95 20.01 1108 19(80% (20%))Old wheat 5g 20g - 21.92 2.25 13.0 821.1 -bran (20%) (80%(180827, )0.1% acticidepreserved)Dispelair lg 20g 5g 22.08 2.26 12.12 820.6 -CF58 (80% (20%)) 11 Table 4 Different concentrations of pre-treated wheat bran and CTMP pulp.

Different amounts of pre-treated wheat bran was used in the experiments belowdemonstrated in Table 5. The wheat bran was pre-treated in the standard way byhomogenizing for 30 min using an lka Ultra Turrax at 17.000 rpm with a sodiumhydroxide concentration of 0.5%. Different amounts of this pre-treated wheat branbatch was used with CTMP according to the table below. A strength increase isobserved with up to 50% wheat bran. Then the strength goes down. Foaming is alsoincreased with increasing wheat bran amount. A too high wheat bran fraction (99%)makes the material too weak and the final hand sheet could not be removed from thepaper making wire without falling apart. A drop in weight of the produced hand sheetswas also observed. This is caused by the increasing amount of soluble products that do not adsorb to the cellulose fiber.

% Wheat bran CTPM Wheat Weight (g) Strain at Stress at Young's Comment(g) bran (g) peak (%) peak (MPa) modulus(MPa)0 25 0 24.14 2.14 11.21 7605% 23.7 1.25 23.65 2.10 12.66 8035 % 22.5 2.5 23.16 2.04 14.20 93020% 20 5 21.92 2.6 17.42 98950% 12.5 12.5 18.89 2.77 25.6 1482 Foaming75% 6.25 18.75 16.19 1.98 14.94 1064 Foaming99% - - - - - - Sample too weak Table 5 Pre-treated oat husk powder and the formation of birch kraft pulp composites. 12 Pre-treatment of oat husk was performed in a similar way as the pre-treatment of wheat bran to prepare the bioadditive grinded oat husk in the form of fine powder was mixed in 0.75%NaOH at a water solid ratio of 8:1. Oat husks were grinded to oat powder prior to use but could also be used as mixing was performed using an Ultra Turrax for 30 min. 12.5 g (dry weight) of this slurry was mixed with 12.5 g of the birch pulp and disintegrated as described in the previous sections. Hand sheets were produced as described and mechanical properties were measured. The Tables 6 and 7, below, describe the ingredients for each sample.

Foaming was observed during the usage of oat powder.__Therefor a commercially available defoamer was used in these__;g Amount birch pulp (g) Oat powder Additive 11 12.5 g 112.5 g pre-treated oat powder (12.5 g dry weight) lg Dispelair CF562 12.5 g 12.5 g oat powder lg Dispelair CF563 12.5 g 225 g pre-treated oat powder (25 g dry weight) lg Dispelair CF56337 g pre-treated oat powder (37 g dry weight, washed4 12.5 g and decanted 4 times, solids mixed with birch kraft pulp) lg Dispelair CF56Table 6Strain (%) Stress (Mpa) Young's modulus (Mpa)Blank (birch) 2.35 19.21 1415.71 5.84 33.42 14712 3.69 10.97 6163 5.39 25.51 10844 4.19 14.73 695Table 7 A strength increase is observed in Table 5 with using 50% pre-treated oat husk powder. ln conclusion, the invention described here is a biocomposite material based on wheat bran and/or oat husk and cellulose. ln addition to lowering the costs due to lower usage of fibers an increase in mechanical properties can be obtained by the different pre- treatments, especially the alkaline ones.

Claims (8)

1. _ A biocomposite material comprising cellulose fibers and a bioadditive fromcereal husks or characterized in that the material is free from anyadditional binder such as butadiene copolymers, acrylates, vinyl copolymers ;~3._§__<§acrylic, styrenated acrylics, polyvinyl acetate, vinylacrylics, ethylenevinyl acetate, styrene butadiene, polyvinyl chloride and ethylene/vinylchloridefs, epoxy, polyester or phenolic resins and isocyanates, and »ifëthat the material is made from a process comprising the steps of: (a) mixing the husk or bran with an aqueous alkaline solution, »sj-with a pH of atleast 7,) and stirring and/or homogenizing with a rpm of 30000 or less,preferably at 5000 to 30000 rpm in order to provide a bioadditive; (b) admixing the bioadditive with a dispersion of cellulose pulp to provide abiocomposite; and (c) thermoforming the biocomposite material with a moulded pulp processcomprising compressing the biocomposite material in a mould at anelevated temperature and at an elevated pressure, thereby curing saidbiocomposite material, whereby the resulting biocomposite material obtainsat least the same strength as the corresponding material comprising thesame cellulose fibers in the same amount, but without the bioadditive, , __.W_.\\_..._ .w LW _.\ ;.\=,.\_.\_. WWflüi>\v~i\<'\\i .ut I ku» >'\\~\\^)) :;::>f“::tš?;;, and wherein the strength is measuredas at least one of strain at peak (%), stress at peak (%) and Young'smodulus (MPa). _ The biocomposite material according to claim 1, comprising a bioadditive derived from at least one of wheat brans and oat husks. The biocomposite material according to claim 1 or 2, comprising 75% (wt) orless of the bioadditive, preferably 5 to 50% (wt). _ The biocomposite material according to claim 1, prepared by a process comprising collecting the water soluble fraction of the bioadditive from step (a)and admixing it with the dispersion of cellulose pulp in step (b). _ The biocomposite material according to claim 4, prepared by a process, wherein the ratio of cereal husk or bran to aqueous solution in the mixing step(a) is from at least 1:1 to 1:100, preferably 1:3 to 1:20 most preferably 1:5 to1:10. _ The biocomposite material according to any one of claims 4 or 5, prepared by a process, wherein the bioadditive is 75% (wt) or less, preferably 5 to 50% (wt) of the mixture of bioadditive and cellulose pulp in the admixing step (b). _ The biocomposite material according to any one of claims 4 to 6, prepared by a process, wherein the alkaline solution of step (a) comprises at least 0_5%(wt) NaOH, preferably 0.5 to 5% (wt) NaOH_ _ The biocomposite material according to any one of claims 4 to 7, prepared by a process comprising adding an additive in at least one of step (a) and step (b)said additive being selected from at least one of cationic starch; AKD(alkylketene dimer); ASA (alkenylsuccinic anhydride); PLA (poly lactic acid);dyes; fillers; pigments; wet strength increasing agents; defoamers;preservatives; and biocides.